Is it an alternate history, then? No: There is no fork in the road that makes the world other than it has become. Whatever is different differs only to the point that it shows that nothing, ultimately, changes. Rather I would call it a speculative history, in the etymological sense: A mirror (speculum) that shows the present its imminent (immanent) future in a past masquerading as falsehood.
The text name-checks Hegel and even has prolonged indirect quotations of Marx, but its basic ontology is the "racial realism" of Critical Race Theory: Whiteness as property, racism as ingrained, the counterstory as resistance. Thus a philosophy even more distinctively American than pragmatism, underlying a novel even more American than Dos Passos's U.S.A. trilogy. And every few pages, one encounters a passage as stunning as this:
Stories splinter in all directions, the hurt Tabbs doesn't see far away. Black bodies burned. Black bodies hanging from trees and telegraph poles. Africans pulled off random streetcars and mobbed to death. Bloated black bodies floating in canals, rivers, and ponds. Blood in every eye. Such stories become commonplace. Tabbs bears these facts with equanimity, nothing so barbarous that the human mind cannot accept it.
(Because of its fantastic elements, I will be nominating it for the Hugo, though I suspect I am the only person who will.)